A choke is a constriction located near the muzzle of a shotgun barrel that changes the patterning characteristics of a shot charge. Chokes have been used in firearms, and in particular shotguns, for many years to vary the percentage of pellets that will hit a given area of a target at a fixed distance from the muzzle. Some gun barrels have fixed chokes. Many shotguns utilize removable choke tubes so that the shooter can vary the shot pattern according to the game being hunted or the type of target shooting involved.
Removable chokes permit one shotgun to be used for a variety of shooting applications. For example, tight, i.e., smaller exit diameter, chokes are used to maintain a high percentage of the shot charge in a tight pattern at longer distances from the muzzle of the shotgun. This characteristic is desirable for long-range shooting situations encountered when, for example, hunting waterfowl. Tight chokes may also be desirable for some forms of trap shooting. At the other end of the spectrum, a wide shot dispersion may be desirable for short-range shooting situations such as skeet shooting.
The versatility provided by removable chokes involves certain tradeoffs. Many modern choke tubes are threaded inserts, which are secured in shotgun barrel muzzles by using approximately 0.5 inches of very fine, continuous threads. The selection of this thread style is necessitated by the limited wall thickness available for this threaded connection, and the need for a secure installation. A certain amount of thread engagement is required to help ensure that the choke tube will not loosen extensively or be expelled from the barrel during firing. To this end, many choke tubes are provided with continuous threads on their exterior surfaces. The barrel has a corresponding set of continuous threads located on its inner surface. Given this design configuration, a choke tube may require upwards of 20 revolutions for complete insertion or extraction. This process is time-consuming.
Some prior choke tubes have interrupted threads, which speed up the process by which the choke tube is threaded into the firearm barrel. Whether the choke tube has interrupted threads or not, there is a tendency for the choke tubes to loosen with use, which would have detrimental effects. Thus there is a need for a removable choke tube that a user may more easily insert and extract from a firearm using fewer revolutions, but that does not lend itself to excessive loosening or expulsion during use.